Tungsten electrode



C. PFANSTIEHL.

TUNGSTEN ELECTRODE.

APPLICATION FILED JUNE 14. 1911.

1 ,32%,@ 11. @o Patented Nov. 25, 1919.

F1211 vvFIETE TNUENT DE EL FHNETIEHL CARL PFANSTIEHL, 0F HIGHLAND PARK, ILLINOIS, ASSIGNOR TO PFANSTIE-HL COMPANY, INC., OF NORTH CHICAGO, ILLINOIS, A CORPORATION OF NEW 7 YORK.

TUNGSTEN ELECTRODE.

Specification of Letters Patent. Patented Nai 25, 1919.

Application filed June 14, 1917. Serial No. 174,821.

To all whom it may concern:

Be it known that I, CARL PFANSTIEHL,

a citizen of the United States, residing at Highland Park, in the county of Lake and State of Illinois, have invented a certam new and useful Improvement in Tungsten Electrodes, of which the following is a full,

or is causedto pass from one contact to another through a gap.

Tungsten may be made in solid form by merely sintering a disk made up of compressed tungsten powder but it has been found that electrodes made of this metal are subject to comparatively rapid deterioration under the action of an electric spark. In order to produce tungsten which will properly withstand the action of the electric spark a sintered body of tungsten must be worked from its sintered condition to a size or diameter about one-half that at which it was originally sintered. Satisfactory electrodes cannot be produced by merely swag ing a disk .of tungsten, that is, a tungsten disk in the condition in which it is taken from the sintering furnace cannot be made into a satisfactory contact merely by hammering or rolling. The best tungsten electrodes are those sawed from the end of rods which have been reduced by a swaging process from an ingot of at least twice the diameter of the rod.

The immense volume of current required to sinter tungsten and the difficulty in sintering large bodies of tungsten resulting from the large amount of current required and from the fragility of rods of tungsten powder and from the difficulty in securing a sufiicient pressure to properly compress a large quantity of tungsten powder into a single ingot have prevented the economical manufacture of worked tungsten rods in sizes more than one-quarter of an inch in diameter. I v

The principal utility for large tungsten electrodes is in supplying a permanent spark gap for wireless telegraph apparatus. Electrodes for this purpose are made from onehalf of an inch to an inch and a half in diameter. The tungsten is mounted on a backing of some good heat conducting ma terial, this .backing being intimately connected with large copper terminals which are provided with heat radiating disks. My invention consists in making up the surface of a large tungsten. disk of a plurality of small tungsten disks, each intimately connected with the heat conducting back, each of the small disks being made of worked tungsten, and each being cut from the end of a tungsten rod so that the end grain of the tungsten is presented to the spark surface. This may necessitate a slightly larger general dimension for the large electrode if round tungsten disks are used, but if hexagonal disks are used the general dimensions of the large electrode will not be materially increased. a

My invention is illustrated in the accompanying drawings'in which,

Figure l is a face View of an electrode made up of circular tungsten disks;

Fig. 2 is a side view of the same electrode showing the screwthreaded mounting;

Fig. 3 is a face view of an electrode made up of hexagonal disks; and

Fig. 4 is a partially sectioned view of the spark gap apparatus such as is used for wlreless telegraph outfits.

In Figs. 1 and 2 the circular disks 6, sawed from the ends of worked tungsten rods, are secured to the mounting 7, which is preferably made of a good heat conduct ing material such as Monel metal, by means of a welding material 8, which is preferably pure copper. In attaching the disks 6 to the metal backing 7 a thin washer of copper is laid upon the face of the backing 7. The tungsten disks 6 are then arranged in form upon the copper washer and a second copper washer is laid upon the 7 upper surface of the disks. The electrode thus assembled is placed in an electric furnace in an inert atmosphere and heated to a temperature at which the copper becomes very fluid. The tungsten disks sink in the molten copper and the disk of copper which was laid upon the upper surface of the disks melts and runs into the interstices between the disks, filling them substantially to the level of the thickness of thedisks. After removing the electrode from the welding furnace the contact face is ground on a surface grinder to remove all, of the copper from the exposed face of the small electrodes roe and to level off any of'the electrodes which may have been slightly tilted during the welding process. The metal constituting the electrode backing is then coated with wax, or other acid resisting material, and the entire body is submerged in nitric acid. The acid attacks the copper, but does not attack the tungsten. The body is allowed to remain in the acid until the copper has been eaten away to a depth slightly more than half the thickness of the tungsten electrodes. Inthis Way each tungsten electrode is inti mately embedded in copper and the copper is intimately united with the backing so that heat is readily conducted from the tungsten disks to the backing.

In Fig. 3 the surface of the electrode is made up of hexagonal disks'of tungsten 9. The procedure in making this disk is the same as that for making the disk illustrated in Figs. 1 and 2, excepting that but one copper washer or disk is used, that being placed between the tungsten disks and the backing.

In the apparatus illustrated in Fig. ithe tube or housing 11 is preferably made of bakelite, or some other good insulating material. The end members 12 and 13 are made of any suitable metal, while the electrodes 14 and 15 and the radiating disks 16 and 17 are preferably made of copper so that the heat produced at the spark gap will be quickly conducted away from the tungsten. An adjusting wheel 17 is provided for one of the electrodes, this electrode being threaded in the member 12 so that the spark gap may be delicately adjusted.

Although I have shown and described my invention with reference to a specific arrangement of parts, it is to be understood that the invention is not to be unduly limited thereto.

Having thus described my invention, what 3. A large tungsten electrode comprising a plurality of small worked tungsten disks mounted upon a single backing and substantially covering said backing, the said disks having their Working faces terminating in the same plane.

' 4. A tungsten electrode comprising a heat conducting backing and a plurality of tungsten disks mounted on said backing in heat conducting relation therewith, with the grain of the metal extending perpendicularly to the faces of said disks.

An electrode con'iprising a large metal backing substantially covered by a plurality of small disks of worked tungsten secured in heat conducting relation therewith.

In witness whereof I hereunto subscribe my name this 6th day of June, A. D. 1918.

CARL PFANSTIEHL.

Witnesses:

IRENE SCHUMANN, WM. OSCAR BELL. 

